The stability of oil-in-water emulsions is affected adversely by a number of different changes that may occur in the structure of these emulsions as time progresses.
There are basically five ways in which the structure of an emulsion of liquid droplets in a continuous medium can change:
1. Creaming/Sedimentation: No change in droplet size (or droplet size distribution), but build-up of an equilibrium droplet concentration gradient within the emulsion. This phenomenon results from external force fields, usually gravitational, acting on the system. “Creaming” is the special case in which the droplets collect in a concentrated layer at the top of an emulsion. “Sedimentation” occurs when the droplets collect in a concentrated layer at the bottom of the emulsion.                2. Flocculation: Again, no change in basic droplet size or distribution but the build-up of aggregates of droplets within the emulsion. The individual droplets retain their identity. This process of flocculation results from the existence of attractive forces between the droplets.        3. Coalescence: Flocculated droplets in the bulk of the emulsion, or alternatively, droplets within a close-packed array resulting from sedimentation or creaming, coalesce to form larger droplets. This results in a change of the initial droplet size distribution. The limiting state here is the complete separation of the emulsion into the two immiscible bulk liquids. Coalescence thus involves the elimination of the thin liquid film (of continuous phase) which separates two droplets in contact in an aggregate or a close-packed array. The forces to be considered here are therefore the forces acting within thin-liquid films in general.        4. Ostwald ripening: An alternative way in which the average droplet size in an emulsion can increase, without the droplets coalescing, occurs if the two liquids forming the disperse phase and the continuous phase, respectively, are not totally immiscible. This is the case in reality because all liquid pairs are mutually miscible to some finite extent. If one starts with a truly monodisperse emulsion system, then no effects arising from this mutual solubility will arise. However, if the emulsion is polydisperse, larger droplets will form at the expense of the smaller droplets owing to the process known as Ostwald Ripening. In principle, the system will tend to an equilibrium state in which all the droplets attain the same size (this may be, of course, that state when we have just one single large drop). The process of Ostwald ripening results from the difference in solubility between small and large droplets.        5. Phase inversion: A further way in which the structure of an emulsion may change is for the emulsion to “invert”, e.g. for an o/w emulsion to change to a w/o emulsion. This may be brought about by a change in temperature or concentration of one of the components or by the addition of a new component to the system.        
The four main processes involved in emulsion destabilization are creaming (sedimentation), flocculation, coalescence and Ostwald Ripening. In practice, all four processes may occur simultaneously or sequentially in any order, depending on the relative rate constants for these processes under the conditions of storage of the emulsion.
If oil-in-water emulsions are stored for prolonged periods of time under varying temperature conditions, as is the case for retail products such as dressings and mayonnaise, the aforementioned destabilizing processes have to be slowed down. In order to achieve this, emulsifiers and/or water thickeners are commonly employed as structuring ingredients in these emulsions. Such emulsifiers usually have an HLB of greater than about 8.0. Examples of such emulsifiers include lecithins, PEG esters and proteins. Examples of water structurants include modified celluloses, starches (modified or non-modified), gums such as xanthan, agar, gelatin, carrageenan (iota, kappa, lambda), Gellan, galactomannans (guar, tara, cassia, LBG), konjac glucomannan, gum arabic, pectins, milk proteins, alginate, chitosan and cellulosic fibres.
However, the use of emulsifiers and water-structuring agents in edible oil-in-water emulsions has the disadvantage that consumers regard many of these ingredients as undesirable additives. Also, the use of these ingredients, e.g. in the form of egg yolk, can represent a substantial cost factor. Hence, it would be desirable if stable oil-in-water emulsions could be produced without or with fewer additives in the form of emulsifiers or water-structuring agents.
Chickpea mayonnaise is an oil-and-water emulsion that is made from chickpeas, oil, vinegar and other ingredients. A known recipe of chickpea mayonnaise is shown below:    1 medium onion, diced into 1-in. pieces    1 large garlic clove, crushed    ¼ c. Spanish sherry vinegar, or cider vinegar, and more for later    ½ tsp. freshly ground black pepper    ½ tsp. ground cumin    ½ tsp. sweet paprika (Spanish if possible)    Generous pinch hot red pepper flakes    1 (15-oz.) can chickpeas, rinsed and drained    ¼ c. tightly packed fresh basil leaves, and more if needed    ¼ to ⅓ c. good-tasting extra-virgin olive oil    Salt to taste
A chicken pea mayonnaise can be prepared on the basis of this recipe by combining the onion, garlic, vinegar, black pepper, cumin, paprika and red pepper in a glass or pottery bowl; covering the bowl with a paper towel and microwaving at high power for 3 minutes; and letting the contents cool while preparing the other ingredients. In a food processor or blender, the chickpeas, basil and olive oil are combined starting with the smallest amounts. Next, the cooled vinegar-onion mixture is added and puréed. Salt, addition vinegar and seasonings may be added to taste and the total mixture is puréed until it is very smooth.
WO 01/52670 describes a food product comprising a starch and protein derived from a pea or lentil flour, wherein the flour starch has been at least partially gelatinized and the flour protein has been at least partially denatured and coagulated. Protein coagulation is achieved by inclusion of a protein coagulating agent, especially a calcium or magnesium salt.
US 2001/0026829 describes a semifluid, binding foodstuff composition for seasoning and/or coloring, comprising an oil-in-water emulsion of a food grade oil and water and (i) ungelatinized starch and (ii) a vegetable powder and/or fruit powder in a finely divided form containing cell wall and/or fiber, wherein the starch and vegetable powder and/or fruit powder are not completely soluble in the water phase. Vegetable powders or fruit powders which are suitable are, in particular, a vegetable concentrate, pea flour, lentil flour, tomato puree, garlic powder, paprika powder, onion powder, mushroom powder, asparagus powder or apple concentrate. The content of the vegetable powder or fruit powder in the foodstuff is generally 10-50% by weight.
EP-A 2 183 983 describes a pourable dressing composition comprising natural fiber derived from minimally processing at least one whole fruit or whole vegetable, wherein the whole fruit or whole vegetable, before minimally processing, contains at least about 25 percent fiber;
wherein the whole fruit or whole vegetable, before minimally processing, is obtained in, or converted to, (1) a dehydrated form and (2) a powdered form having an average particle size of less than about 500 microns;
wherein the dehydrated and powdered form of the whole fruit or vegetable is minimally processed using an enzymatic treatment to reduce the initial viscosity without shear to less than about 12,500 cP;
wherein the enzymatically treated whole fruit or vegetable is incorporated into a pourable dressing base composition to form the pourable dressing composition containing at least 2.5 grains total fiber per single serving of the pourable dressing composition.
The fiber may be derived from whole vegetables that are high in fiber, such as beans, carrots, broccoli and the like. Example 4 of EP-A 2 183 983 describes a dressing comprising:    72.5 wt. % of an enzyme treated lupin bean slurry (31.67% w/w);    15 wt. % soybean oil;    2 wt. % salt;    5 wt. % sucrose;    4 wt. % vinegar;    0.4 wt. % phosphoric acid (85%);    1.1 wt. % water.